Who Owns the Sky? is about an important but largely forgotten legal problem in the early years of flight. English and American common law had always said that landowners owned the airspace above their land, with no height limit. As the ancient maxim put it, cujus est solum ejus est usque ad coelum – he who owns the soil owns up to the sky. If that remained true, the new airplanes would have nowhere to fly, because they would be trespassing almost everywhere they went. The government couldn’t simply take the airspace away from landowners and give it to pilots without violating the constitution, lawyers worried, because airspace was a kind of property, and a taking of property required compensation. So how would the planes ever get off the ground?

The issue was intertwined with all sorts of broader questions being debated at the time, some of which had to with the nature of the common law itself. Where exactly did the common law come from? Was it something judges found or something they made? And how did it change? Page 99 comes near the end of a chapter about these questions.

Condemning the airspace, however, would have been an enormous administrative burden. R. Floyd Clarke shuddered at the prospect of “the description in a petition of condemnation of all the parcels of real estate throughout the State and notice to all the owners, mortgagees, etc.” Just notifying the landowners, Clarke despaired, would be “a stupendous and almost impossible undertaking.” And even if that hurdle could have been mounted, condemnation might well have required separate hearings, and possibly even jury trials, for each individual landowner, at which each would have the opportunity to establish the amount of loss that he or she would individually suffer from overflights. For anyone who gave thought to the time and expense that would be involved in condemning enough airspace to allow commercial air travel, the use of the state or federal government’s eminent domain power was not an attractive option. Promoters of aviation were back to the constitutional problem. A statute abrogating the cujus est solum maxim, by allowing aviators to fly over private land, ran a considerable risk of being held unconstitutional.

This was why lawyers in the 1910s and 1920s paid so much attention to the common law. Because of the fiction that judges did not make the law but found it, a judicial determination that aviators could fly over private property was not susceptible to constitutional challenge. If a judge, rather than a legislature, were to modify the cujus est solum maxim, the surface discourse of the legal system would not deem him to be changing the law at all. He would instead be understood to be discerning what the law had always been.